You brought up Unit 731.
The people who ran Unit 731 were tried by the Russians, not the Americans. In fact, the Americans (the Good Guys) went so far as to protect the psychopaths who ran it from any prosecution.
So how bad were they, really, if the Good Guys took pains to protect them?
So what concessions would you have made to the Japanese?
They already tacitly understood (it had been communicated through "backchannels") that they could retain their Emperor (though he would have to renounce godhood).
So what else would you have conceded to them, to "sweeten the pot" and induce them to surrender?
The Japanese fascists were morally on a par with the Nazis - and we had demanded the unconditional surrender of Germany. For what possible reason should we have accorded Imperial Japan better conditions than Nazi Germany?!
Regards,